Correlated ESR, PL and TL studies on K 3Na(SO 4) 2 : Eu thermoluminescence dosimetry phosphor

Abstract

Strong thermoluminescence (TL) was observed in K 3Na(SO 4) 2 : Eu phosphor in the Eu doped K 2SO 4–Na 2SO 4 system. The defect centres formed in this TL phosphor are studied using the technique of electron spin resonance. Two glow peaks at 423 and 475 K are observed in K 3Na(SO 4) 2 : Eu phosphor prepared by the melt method. The peak 475 K is shown to be at least thrice as sensitive as the conventional CaSO 4 : Dy phosphor used in the TL dosimetry of ionizing radiations. Two centres, assigned to SO 4 − and SO 3 −, are observed at room temperature in the melt prepared phosphor. Step annealing measurements showed a connection between these centres and the observed TL glow peaks. Three TL glow peaks at 360, 423 and 453 K are observed in the K 3Na(SO 4) 2 : Eu phosphor prepared by the evaporation method. A SO 4 − centre and two different SO 4 − centres are observed in this phosphor. TL and photoluminescence emission spectra indicate that the europium ion is in the divalent state in K 3Na(SO 4) 2 : Eu phosphor.